1. Field of the Invention
The invention disclosed herein relates to series regulators.
2. Description of Related Art
FIG. 17 is a diagram showing one example of a conventional series regulator. In the series regulator 20 of this conventional example, an operational amplifier 21 controls a gate signal G1 for an output transistor M1 so that a feedback voltage Vfb (a division voltage of an output voltage Vout) equals a reference voltage Vref. With this, it is possible to generate from an input voltage Vin a desired output voltage Vout (=[(R1+R2)]/R2)×Vref).
One example of the conventional technology just mentioned is seen in Japanese Patent Application published as No. 2008-043086.
However, the conventional series regulator 20 mentioned above covers the entire region of a load range using a single operational amplifier 21 and a single output transistor M1. Thus, it is difficult to achieve stable operation in a wide load range and fast load response combined with low current consumption.